From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Letter discussing steering gear ratios, roller bearings, and the Marles-Weller Steering Gear.
| Identifier | ExFiles\Box 28\2\ Scan035 | |
| Date | 11th August 1932 | |
| Messrs. Rolls-Royce Ltd. Contd 2. 11.8.32. Gear in the straight ahead position is just under 10½°, but we can of course reduce this angle by cutting a slightly lower gear ratio, and we should be pleased to do this in the case of making up a sample gear for you to test. In this connection we would say that our standard gear ratio in the R7 Gear is such that 3¼ turns of the wheel are required to move the drop arm through 65°, making the gear ratio exactly 18 to 1. If the Cam were cut to give 3¼ turns of the wheel for the same drop arm movement, then this would give a helix angle of 9°, which we think would probably be satisfactory in the case of your vehicle. It is, however, quite impossible to foretell the exact performance of a steering on a vehicle, as we find that the performance varies on vehicles of different make, and is dependent on a number of things outside the actual steering box. The use of Roller Bearings, as fitted in our latest type of gear, does introduce a certain amount of damping in that these rollers are parallel rollers, and consequently slip is present. This has been found to have a good effect on the characteristics of the gear, and is one of the particular reasons for our having adopted the same. It must be recognised, however, that the Marles Steering is a very high efficiency gear, and as such is possibly more susceptible to inaccuracies of steering lay-out than some other types of gears, and in this connection perhaps our latest development in Steering Gears, viz. the Marles-Weller Gear may be of interest to you. We are enclosing herewith a general arrangement drawing of our "Q" Type Marles-Weller Steering Gear, our GA.2425 for your examination, and we are also enclosing a booklet illustrating and describing this gear. You will note that the gear is designed to give a considerable area of contact at the point of juncture between the cam track and the four hemispheres embedded in the follower. The Marles-Weller Gear employs sliding movement in the - 2 - | ||